In the field of back panel wiring, it is typical that the computer frame manufacturer makes available, for interconnect purposes, a matrix of terminal posts or pins supported by and electrically connected to a computer input/output (I/O) PCB. The user is thereby given several options to interconnect his system to the computer, e.g., so-called wire/wrap connection, discrete wire soldering, press-fit of female connectors thereon, etc. In the last-mentioned option, the user typically enshrouds a selected array of the posts with a header which is designed, on the one hand, to frictionally receive the posts to obtain self-securement of the header to the PCB and, on the other hand, to guide the female connector into properly polarized relation with the post array such that individual female connector sockets register with individual posts of the array and resiliently electrically engage same.
Two interdependent force relationships attend the self-securement of headers to PCBs, namely, insertion force and withdrawal force. Desirably, insertion force, i.e., the force needed to apply the header to the posts, would be low for post and PCB protection and for assembler convenience. Conversely, relatively high withdrawal force is desired to insure that the header maintain its assembled relation with the PCB and not be accidentally displaced. Considering, for example, a ten-post array arranged with two rows of five posts, a thirty-five-pound header withdrawal force is typically desired. On the other hand, the per post header insertion force should typically not exceed one and seven-tenths pounds, lest the posts be pushed out of retention in the PCB. The insertion force criterion of seventeen pounds total gives rise to a disparity of eighteen pounds between the respective desired insertion and withdrawal forces. Further, the withdrawal force decreases on cycling since the header channels for frictional receipt of the posts become enlarged and afford less retentive force.
One known practice for compensating for the disparity noted above as between insertion and withdrawal forces and for providing constancy of withdrawal force over cycling has been to introduce metal spring clips in retaining relation to the posts within the header. However, this practice not only increases costs of header manufacture but also can give rise to electrical shorting problems if the clips become dislodged within the header.
Presently known headers also include retainers to secure connectors therein, customary retainers being in the form of members supported by the header for movement into such position as to block egress of the connector from the header. Some headers arrange these retaining members such that they function as above in one sense of movement but also serve the function of ejecting the connector from the header upon opposite sense movement in the header.
As headers are presently known in the art, they are deemed to have shortcomings in respect of the interdependence of insertion and withdrawal forces, absent such interior metal spring clips, and in requiring fully separate structure for the functions of header securement to the PCB, of connector retention and of connector ejection.